Make blender unaware of user/system installed add-ons
In my customized, local install I needed to create an empty config/ folder inside the 2.XX/ folder (the one that contains datafiles/, python/, scripts/ already - in my case 2.67/). As soon as blender sees this folder it completely ignores any user/system add-ons (and everything else too I suppose - startup files, configuration, etc.)

I found the answer here: Need guidance for creating no dependancies between two installs of Blender